Column alias not recognized in WHERE-statement

Question

I have a strange 'problem' with one of my created queries. Given the next query:

 SELECT 
 ID,
 DistanceFromUtrecht,
 (
  SELECT
   (MAX(DateUntil) - (ReleaseDays * 60 * 60 * 24))
  FROM
   PricePeriod
  WHERE
   PricePeriod.FK_Accommodation = Accommodation.ID
 ) AS LatestBookableTimestamp
FROM
 Accommodation
WHERE
 LatestBookableTimestamp < UNIX_TIMESTAMP()

phpMyAdmin keeps throwing an error about not having a column named 'LatestBookableTimestamp', even allthough I've a column, retreived by a subquery, that alias. I've also tried it selecting every column with the tableprefix. This didn't work eighter. Finally I've selected all columns by a table-alias and I gave the table an alias. All with no luck.

Can someone tell me what I'm doing wrong? I've even searched for some resources to see if I'm not mistaken, but in many cases authors on the internet use the same syntax as I do.

Answer 1

Use HAVING

HAVING
  LatestBookableTimestamp < UNIX_TIMESTAMP()

On a side note, you're using a dependednt subquery, which is a bad idea performance wise.

Try like this:

SELECT 
  a.ID,
  a.DistanceFromUtrecht,
  pp.LatestBookableTimestamp
FROM
  Accommodation AS a
INNER JOIN (
  SELECT
    FK_Accommodation,
    MAX(DateUntil) - (ReleaseDays * 60 * 60 * 24) AS LatestBookableTimestamp
  FROM 
    PricePeriod 
  GROUP BY 
    FK_Accommodation
) AS pp    
ON pp.FK_Accommodation = a.ID    
WHERE
  pp.LatestBookableTimestamp < UNIX_TIMESTAMP()